Optimizing Waste for Energy: Exploring Municipal Solid Waste Variations on Torrefaction and Biochar Production

Energy primarily comes from fossil fuels, which leads to environmental deterioration through increased carbon dioxide load and other greenhouse gases in the atmosphere. Renewable energy is a cheap alternative, and biomass, like municipal solid wastes (MSWs), can be suitably used for energy production. This paper reviews the impact of variations in MSW composition on its physical, chemical, and lignocellulosic properties. It further illustrates how these properties affect torrefaction products. It was observed that MSW can refer to either a combination of different waste types or independent wastes; hence, there is no standard composition of MSW. The variations in composition are responsible for fluctuating physical, chemical, and lignocellulosic properties. These properties, along with torrefaction process parameters, simultaneously affect the torrefied product, whereas lignocellulosic properties influence the biochar yield, and physical and chemical properties impact calorific value and ash content. Torrefying MSW containing low moisture content yields biochar with a high calorific value. Methods to improve the lignocellulosic properties of MSW have not been studied. Research is needed to assess the possibility of improving biochar yields in MSW by enhancing lignin percentages, possibly through blending MSW. A guide on the best blend combinations and ratios is required. Also, it is crucial to study optimal torrefaction process parameters.